Add type parameters to vi.fn() mocks for oxlint 1.60 vitest rule

oxlint 1.60 enables vitest/require-mock-type-parameters by default,
which requires explicit type parameters on all vi.fn() calls.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/components/__tests__/EventList.spec.ts

@@ -2,11 +2,12 @@ import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
 import { mount, flushPromises } from '@vue/test-utils'
 import { createRouter, createMemoryHistory } from 'vue-router'
 import EventList from '../EventList.vue'
+import type { api } from '../../api/client'
 
 vi.mock('../../api/client', () => ({
   api: {
-    PATCH: vi.fn(),
-    DELETE: vi.fn(),
+    PATCH: vi.fn<typeof api.PATCH>(),
+    DELETE: vi.fn<typeof api.DELETE>(),
   },
 }))
 
@@ -31,7 +32,7 @@ const mockEvents = [
   { eventToken: 'rsvp-1', title: 'Attending Event', dateTime: '2026-03-11T20:00:00', rsvpToken: 'rsvp-token', rsvpName: 'Max' },
 ]
 
-const removeEventMock = vi.fn()
+const removeEventMock = vi.fn<(eventToken: string) => void>()
 
 vi.mock('../../composables/useEventStorage', () => ({
   isValidStoredEvent: (e: unknown) => {